Add support for rustc --check-cfg well known names and values

src/cargo/core/compiler/context/mod.rs

@@ -225,6 +225,7 @@ impl<'a, 'cfg> Context<'a, 'cfg> {
                 let mut args = compiler::extern_args(&self, unit, &mut unstable_opts)?;
                 args.extend(compiler::lto_args(&self, unit));
                 args.extend(compiler::features_args(&self, unit));
+                args.extend(compiler::check_cfg_args(&self, unit));
 
                 let script_meta = self.find_build_script_metadata(unit);
                 if let Some(meta) = script_meta {

src/cargo/core/compiler/mod.rs

@@ -646,6 +646,7 @@ fn rustdoc(cx: &mut Context<'_, '_>, unit: &Unit) -> CargoResult<Work> {
 
     rustdoc.arg("-o").arg(&doc_dir);
     rustdoc.args(&features_args(cx, unit));
+    rustdoc.args(&check_cfg_args(cx, unit));
 
     add_error_format_and_color(cx, &mut rustdoc);
     add_allow_features(cx, &mut rustdoc);
@@ -966,6 +967,7 @@ fn build_base_args(
     }
 
     cmd.args(&features_args(cx, unit));
+    cmd.args(&check_cfg_args(cx, unit));
 
     let meta = cx.files().metadata(unit);
     cmd.arg("-C").arg(&format!("metadata={}", meta));
@@ -1039,15 +1041,30 @@ fn build_base_args(
     Ok(())
 }
 
-/// Features with --cfg and all features with --check-cfg
-fn features_args(cx: &Context<'_, '_>, unit: &Unit) -> Vec<OsString> {
-    let mut args = Vec::with_capacity(unit.features.len() + 2);
+/// All active features for the unit passed as --cfg
+fn features_args(_cx: &Context<'_, '_>, unit: &Unit) -> Vec<OsString> {
+    let mut args = Vec::with_capacity(unit.features.len() * 2);
 
     for feat in &unit.features {
         args.push(OsString::from("--cfg"));
         args.push(OsString::from(format!("feature=\"{}\"", feat)));
     }
 
+    args
+}
+
+/// Generate the --check-cfg arguments for the unit
+fn check_cfg_args(cx: &Context<'_, '_>, unit: &Unit) -> Vec<OsString> {
+    if !cx.bcx.config.cli_unstable().check_cfg_features
+        && !cx.bcx.config.cli_unstable().check_cfg_well_known_names
+        && !cx.bcx.config.cli_unstable().check_cfg_well_known_values
+    {
+        return Vec::new();
+    }
+
+    let mut args = Vec::with_capacity(unit.pkg.summary().features().len() * 2 + 4);
+    args.push(OsString::from("-Zunstable-options"));
+
     if cx.bcx.config.cli_unstable().check_cfg_features {
         // This generate something like this:
         //  - values(feature)
@@ -1060,11 +1077,20 @@ fn features_args(cx: &Context<'_, '_>, unit: &Unit) -> Vec<OsString> {
         }
         arg.push(")");
 
-        args.push(OsString::from("-Zunstable-options"));
         args.push(OsString::from("--check-cfg"));
         args.push(arg);
     }
 
+    if cx.bcx.config.cli_unstable().check_cfg_well_known_names {
+        args.push(OsString::from("--check-cfg"));
+        args.push(OsString::from("names()"));
+    }
+
+    if cx.bcx.config.cli_unstable().check_cfg_well_known_values {
+        args.push(OsString::from("--check-cfg"));
+        args.push(OsString::from("values()"));
+    }
+
     args
 }
 

src/cargo/core/features.rs

@@ -639,6 +639,8 @@ unstable_cli_options!(
     config_include: bool = ("Enable the `include` key in config files"),
     credential_process: bool = ("Add a config setting to fetch registry authentication tokens by calling an external process"),
     check_cfg_features: bool = ("Enable compile-time checking of features in `cfg`"),
+    check_cfg_well_known_names: bool = ("Enable compile-time checking of well known names in `cfg`"),
+    check_cfg_well_known_values: bool = ("Enable compile-time checking of well known values in `cfg`"),
     doctest_in_workspace: bool = ("Compile doctests with paths relative to the workspace root"),
     doctest_xcompile: bool = ("Compile and run doctests for non-host target using runner config"),
     dual_proc_macros: bool = ("Build proc-macros for both the host and the target"),
@@ -837,6 +839,8 @@ impl CliUnstable {
             "advanced-env" => self.advanced_env = parse_empty(k, v)?,
             "config-include" => self.config_include = parse_empty(k, v)?,
             "check-cfg-features" => self.check_cfg_features = parse_empty(k, v)?,
+            "check-cfg-well-known-names" => self.check_cfg_well_known_names = parse_empty(k, v)?,
+            "check-cfg-well-known-values" => self.check_cfg_well_known_values = parse_empty(k, v)?,
             "dual-proc-macros" => self.dual_proc_macros = parse_empty(k, v)?,
             // can also be set in .cargo/config or with and ENV
             "mtime-on-use" => self.mtime_on_use = parse_empty(k, v)?,

src/doc/src/reference/unstable.md

@@ -1161,6 +1161,32 @@ For instance:
 cargo check -Z unstable-options -Z check-cfg-features
 ```
 
+### check-cfg-well-known-names
+
+* RFC: [#3013](https://github.com/rust-lang/rfcs/pull/3013)
+
+The `-Z check-cfg-well-known-names` argument tells Cargo to activate `rustc` and `rustdoc` unstable
+`--check-cfg` command line as `--check-cfg=names()`.
+This enables compile time checking of well known names in `#[cfg]`, `cfg!` and `#[cfg_attr]`.
+For instance:
+
+```
+cargo check -Z unstable-options -Z check-cfg-well-known-names
+```
+
+### check-cfg-well-known-values
+
+* RFC: [#3013](https://github.com/rust-lang/rfcs/pull/3013)
+
+The `-Z check-cfg-well-known-values` argument tells Cargo to activate `rustc` and `rustdoc` unstable
+`--check-cfg` command line as `--check-cfg=values()`.
+This enables compile time checking of well known values in `#[cfg]`, `cfg!` and `#[cfg_attr]`.
+For instance:
+
+```
+cargo check -Z unstable-options -Z check-cfg-well-known-values
+```
+
 ## Stabilized and removed features
 
 ### Compile progress

tests/testsuite/build.rs

@@ -6389,3 +6389,89 @@ fn check_cfg_features_with_namespaced_features() {
         )
         .run();
 }
+
+#[cfg_attr(windows, ignore)] // weird normalization issue with windows and cargo-test-support
+#[cargo_test]
+fn check_cfg_well_known_names() {
+    if !is_nightly() {
+        // --check-cfg is a nightly only rustc command line
+        return;
+    }
+
+    let p = project()
+        .file("Cargo.toml", &basic_manifest("foo", "0.1.0"))
+        .file("src/main.rs", "fn main() {}")
+        .build();
+
+    p.cargo("build -v -Z check-cfg-well-known-names")
+        .masquerade_as_nightly_cargo()
+        .with_stderr(
+            "\
+[COMPILING] foo v0.1.0 [..]
+[RUNNING] `rustc [..] --check-cfg 'names()' [..]
+[FINISHED] dev [unoptimized + debuginfo] target(s) in [..]
+",
+        )
+        .run();
+}
+
+#[cfg_attr(windows, ignore)] // weird normalization issue with windows and cargo-test-support
+#[cargo_test]
+fn check_cfg_well_known_values() {
+    if !is_nightly() {
+        // --check-cfg is a nightly only rustc command line
+        return;
+    }
+
+    let p = project()
+        .file("Cargo.toml", &basic_manifest("foo", "0.1.0"))
+        .file("src/main.rs", "fn main() {}")
+        .build();
+
+    p.cargo("build -v -Z check-cfg-well-known-values")
+        .masquerade_as_nightly_cargo()
+        .with_stderr(
+            "\
+[COMPILING] foo v0.1.0 [..]
+[RUNNING] `rustc [..] --check-cfg 'values()' [..]
+[FINISHED] dev [unoptimized + debuginfo] target(s) in [..]
+",
+        )
+        .run();
+}
+
+#[cfg_attr(windows, ignore)] // weird normalization issue with windows and cargo-test-support
+#[cargo_test]
+fn check_cfg_all() {
+    if !is_nightly() {
+        // --check-cfg is a nightly only rustc command line
+        return;
+    }
+
+    let p = project()
+        .file(
+            "Cargo.toml",
+            r#"
+                [project]
+                name = "foo"
+                version = "0.1.0"
+
+                [features]
+                f_a = []
+                f_b = []
+            "#,
+        )
+        .file("src/main.rs", "fn main() {}")
+        .build();
+
+    p.cargo("build -v -Z check-cfg-features -Z check-cfg-well-known-names -Z check-cfg-well-known-values")
+        .masquerade_as_nightly_cargo()
+        .with_stderr(
+            "\
+[COMPILING] foo v0.1.0 [..]
+[RUNNING] `rustc [..] --check-cfg 'values(feature, \"f_a\", \"f_b\")' --check-cfg 'names()' --check-cfg 'values()' [..]
+[FINISHED] dev [unoptimized + debuginfo] target(s) in [..]
+",
+        )
+        .run();
+}

tests/testsuite/check.rs

@@ -1034,3 +1034,53 @@ fn check_cfg_features() {
         )
         .run();
 }
+
+#[cfg_attr(windows, ignore)] // weird normalization issue with windows and cargo-test-support
+#[cargo_test]
+fn check_cfg_well_known_names() {
+    if !is_nightly() {
+        // --check-cfg is a nightly only rustc command line
+        return;
+    }
+
+    let p = project()
+        .file("Cargo.toml", &basic_manifest("foo", "0.1.0"))
+        .file("src/main.rs", "fn main() {}")
+        .build();
+
+    p.cargo("check -v -Z check-cfg-well-known-names")
+        .masquerade_as_nightly_cargo()
+        .with_stderr(
+            "\
+[CHECKING] foo v0.1.0 [..]
+[RUNNING] `rustc [..] --check-cfg 'names()' [..]
+[FINISHED] dev [unoptimized + debuginfo] target(s) in [..]
+",
+        )
+        .run();
+}
+
+#[cfg_attr(windows, ignore)] // weird normalization issue with windows and cargo-test-support
+#[cargo_test]
+fn check_cfg_well_known_values() {
+    if !is_nightly() {
+        // --check-cfg is a nightly only rustc command line
+        return;
+    }
+
+    let p = project()
+        .file("Cargo.toml", &basic_manifest("foo", "0.1.0"))
+        .file("src/main.rs", "fn main() {}")
+        .build();
+
+    p.cargo("check -v -Z check-cfg-well-known-values")
+        .masquerade_as_nightly_cargo()
+        .with_stderr(
+            "\
+[CHECKING] foo v0.1.0 [..]
+[RUNNING] `rustc [..] --check-cfg 'values()' [..]
+[FINISHED] dev [unoptimized + debuginfo] target(s) in [..]
+",
+        )
+        .run();
+}

tests/testsuite/test.rs

@@ -4575,3 +4575,109 @@ fn check_cfg_features_doc() {
         )
         .run();
 }
+
+#[cfg_attr(windows, ignore)] // weird normalization issue with windows and cargo-test-support
+#[cargo_test]
+fn check_cfg_well_known_names() {
+    if !is_nightly() {
+        // --check-cfg is a nightly only rustc command line
+        return;
+    }
+
+    let p = project()
+        .file("Cargo.toml", &basic_manifest("foo", "0.1.0"))
+        .file("src/main.rs", "fn main() {}")
+        .build();
+
+    p.cargo("test -v -Z check-cfg-well-known-names")
+        .masquerade_as_nightly_cargo()
+        .with_stderr(
+            "\
+[COMPILING] foo v0.1.0 [..]
+[RUNNING] `rustc [..] --check-cfg 'names()' [..]
+[FINISHED] test [unoptimized + debuginfo] target(s) in [..]
+[RUNNING] [..]
+",
+        )
+        .run();
+}
+
+#[cfg_attr(windows, ignore)] // weird normalization issue with windows and cargo-test-support
+#[cargo_test]
+fn check_cfg_well_known_values() {
+    if !is_nightly() {
+        // --check-cfg is a nightly only rustc command line
+        return;
+    }
+
+    let p = project()
+        .file("Cargo.toml", &basic_manifest("foo", "0.1.0"))
+        .file("src/main.rs", "fn main() {}")
+        .build();
+
+    p.cargo("test -v -Z check-cfg-well-known-values")
+        .masquerade_as_nightly_cargo()
+        .with_stderr(
+            "\
+[COMPILING] foo v0.1.0 [..]
+[RUNNING] `rustc [..] --check-cfg 'values()' [..]
+[FINISHED] test [unoptimized + debuginfo] target(s) in [..]
+[RUNNING] [..]
+",
+        )
+        .run();
+}
+
+#[cfg_attr(windows, ignore)] // weird normalization issue with windows and cargo-test-support
+#[cargo_test]
+fn check_cfg_well_known_names_doc() {
+    if !is_nightly() {
+        // --check-cfg is a nightly only rustc command line
+        return;
+    }
+
+    let p = project()
+        .file("Cargo.toml", &basic_manifest("foo", "0.1.0"))
+        .file("src/lib.rs", "#[allow(dead_code)] fn foo() {}")
+        .build();
+
+    p.cargo("test -v --doc -Z check-cfg-well-known-names")
+        .masquerade_as_nightly_cargo()
+        .with_stderr(
+            "\
+[COMPILING] foo v0.1.0 [..]
+[RUNNING] `rustc [..] --check-cfg 'names()' [..]
+[FINISHED] test [unoptimized + debuginfo] target(s) in [..]
+[DOCTEST] foo
+[RUNNING] `rustdoc [..] --check-cfg 'names()' [..]
+",
+        )
+        .run();
+}
+
+#[cfg_attr(windows, ignore)] // weird normalization issue with windows and cargo-test-support
+#[cargo_test]
+fn check_cfg_well_known_values_doc() {
+    if !is_nightly() {
+        // --check-cfg is a nightly only rustc command line
+        return;
+    }
+
+    let p = project()
+        .file("Cargo.toml", &basic_manifest("foo", "0.1.0"))
+        .file("src/lib.rs", "#[allow(dead_code)] fn foo() {}")
+        .build();
+
+    p.cargo("test -v --doc -Z check-cfg-well-known-values")
+        .masquerade_as_nightly_cargo()
+        .with_stderr(
+            "\
+[COMPILING] foo v0.1.0 [..]
+[RUNNING] `rustc [..] --check-cfg 'values()' [..]
+[FINISHED] test [unoptimized + debuginfo] target(s) in [..]
+[DOCTEST] foo
+[RUNNING] `rustdoc [..] --check-cfg 'values()' [..]
+",
+        )
+        .run();
+}